Embodiments of the present disclosure relate to a driving circuit for a liquid crystal display (LCD) backlight source.
A CRT display is a display using a Cathode Ray Tube (CRT). Currently, the flat plate display has taken over the market for the conventional CRT display. In particular, the LCD develops fastest. The LCD is attractive to consumers due to its advantages of light weight, thinness, high resolution, high color Gamut, among others. In the recent years, the concepts of low carbon and environmental protection are increasingly becoming hot topics all over the world. Under this circumstance, different technologies are tried in the display field, represented by the LCD, to obtain the object of low power consumption, low carbon, and environmental protection.
With emission efficiency of the LED increasing, the LED has a very long life time, and it per se does not contain element Hg which is very detrimental to the environment. Due to these advantages, the LED is applied in the field of the LCD backlight source more and more broadly. The LCD product with a LED backlight source attracts lots of users due to its light weight and thinness, and the concept of environmental protection. However, it is the thinness of the LED backlight source that requires the circuit driving the LED backlight source with a special form.
The light weight and thinness mentioned above is realized by an edge-typed placing arrangement of the LED lights. In other words, the LED lights are placed at the edge of the display.
In order to make the backlight source even thinner, it is necessary to reduce the width of the LED column, and in view of the current light package, a metal substrate PCB is required for the design. The metal substrate PCB is a single-side PCB, which means wiring on the single side is required. In order to meet the requirement of both the wiring and the width, the LED lights need to be connected in serial under most of the situations. For the serial connection of multiple lights, the voltage is usually around 60˜150V. However, in terms of the current technology for bulk production, normally the input voltage is 24V. As a result, there are two issues: 1). the conversion efficiency at 24V˜150V; and 2). the heat dissipation and the price factor of the key devices such as MOSFET in the LED backlight source.
The existing driving circuit for the back light of the LCD of a large size is designed based on the BOOST structure, which is shown in FIG. 1. As shown in FIG. 1, the conventional BOOST structure is illustrated. At this point, the voltage at Vout is larger than or equal to V1, the voltage waveform of which is shown in FIG. 2. As seen from FIG. 2, the voltage tolerance of the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is around 150V, so a MOSFET with a voltage tolerance of 200V will be chosen. The disadvantages of the circuit are that both the temperature of the circuit board and the Bill OF Material (BOM) of the entire circuit are high, and the current-driving ability of the circuit is low, which means the circuit cannot output a large current, due to devices with a high voltage tolerance such as MOSFET are used.